I don't think so. He's not exactly like the other old Disney characters. They missed the chance to include him in Timeless River or the Classic Kingdom minigames, but probably on purpose because he wouldn't actually fit that much. I don't miss him anyway because I know little about Oswald except the thing about copyright issues with the character. He's nothing but a Mickey with bunny ears to me (or the other way around, I guess).
But I understand that people who have fond memories of him want him to appear in KH.
Now, to be frank Oswald's really more than just a Mickey clone, but what could've been had Disney tried to touch more upon him....(Eh, the olden game Epic Mickey touched upon the topic of Oswald and many other characters no one remembered more. It's a really good game, and had it not been for its sequel it could've flourished more.)
Anyway in regards of Oswald put in the series, it really depends on how he could be portrayed in there. Cameo or main character? To which what would be the point in either catagory?